1. Field of the Invention
This invention relates to a typewriter ribbon cartridge and more particularly to a ribbon cartridge designed to facilitate the advancement of typewriter ribbon during typing.
2. Prior Art
Many typewriters are produced today to accept typewriter ribbon enclosed in a cartridge. Typewriter ribbon cartridges generally include a casing which supports the upper and lower ends of a ribbon receiving spindle and, at a spaced location, the upper and lower ends of a ribbon supply spool. Ribbon is loaded on the supply spool, and during operation of the typewriter, a feed mechanism advances the ribbon from the supply spool to the receiving spindle.
The typewriter ribbon cartridge units presently used, an example being illustrated in U.S. Pat. No. 3,731,781, to Caudill, et al., issued May 8, 1973, have been lacking in a number of respects. Many of these cartridges use a totally enclosed housing which supports the upper and lower ends of the ribbon receiving spindle and the upper and lower ends of the ribbon supply spool. This is generally accomplished by providing a housing having an upper plate with downwardly extending sides which receive a lower cover. Both the ribbon takeup spindle and supply spool are supported between the upper plate and the lower cover.
This arrangement has been satisfactory in some respects. However, both the upper plate and lower cover are stationary relative to the rotative movement of both the takeup spindle and the supply spool. As a result, the bottom edge of the ribbon is continuously drawn over the stationary lower cover as the ribbon is fed from the supply spool to the takeup spindle. This contact between the ribbon and the lower cover of the conventional ribbon typewriter cartridges results in drag on the ribbon causing the ribbon to stretch or bind up during operation of the typewriter. Further, this arrangement prevents the uniform feeding of the ribbon and in some cases may completely restrict the feeding of the ribbon from the supply spool to the takeup spindle.
This conventional arrangement also requires substantial alignment of the ribbon on the supply spool as the ribbon is wound on the spool. If the ribbon is wound too low on the spool, when the supply spool is assembled into the cartridge the ribbon will be in binding contact with the lower cover. When this occurs, substantial drag may result between the ribbon and the cover and prevent the relative movement between the ribbon and the cover necessary for the ribbon to advance during typing.
Further, in the conventional typewriter cartridge design, the ribbon is wound onto the supply spool and then must be assembled into the housing. During assembly, the ribbon is fully exposed and may be easily damaged or dislocated from the spool.